Structures of Angular Pyranocoumarins of Bai-Hua Qian-Hu, the Root of Peucedanum praeruptorum1

Three new angular-type dihydropyranocoumarins, peucedanocoumarin I ( 1), peucedanocou-marin II ( 2), peucedanocoumarin III ( 3), and a known coumarin having the same skeleton, pteryxin ( 4), were isolated from the crude drug "Bai-Hua Qian-Hu" of the Q-II type series, which is the root of PEUCEDANUM PRAERUPTORUM Dunn. (Umbelliferae). The chemical structures of 1, 2, and 3 have been established by physicochemical methods to be 3' ( S)-2-methylbutyryloxy-4'-( R)-acetoxy-3',4'-dihydroseselin, 3'( S)-acetoxy-4'( R)-angeloyloxy-3',4'-dihydroseselin, and 3'( S)-acetoxy-4'( R)-tigloyloxy-3',4'-dihydroseselin, respectively.